A 110-foot dredging barge sank in stormy Lake Huron early Thursday and a tugboat pushing the barge capsized, causing no injuries but spilling an unknown amount of diesel fuel, authorities said Thursday.

It wasn't immediately clear what caused the Arthur J. to sink around 4:35 a.m., the U.S. Coast Guard said. The vessel went down near the southern end of the lake, just over a mile from the Michigan coast and about 65 miles northeast of Detroit.

A crew from the Coast Guard's Port Huron station determined that everyone aboard both vessels was accounted for, said Chief Petty Officer Kyle Niemi of the Cleveland district office.

The dredge has a capacity of 8,000 gallons of fuel but the owner said it was carrying 1,500 to 2,000 gallons when it sank, the Coast Guard said. It's unknown how much escaped, but a roughly 500-foot sheen was visible on the surface.

A containment boom was placed on the water to limit the fuel's spread but bad weather may hinder the cleanup, said Petty Officer Lauren Laughlin.

Niemi said none of the fuel had reached the shore.

MCM Marine Inc., based in Sault Ste. Marie, owns the dredge and the 38-foot tug Madison. The company has hired a contractor to handle the cleanup, which the Coast Guard will monitor.

Both vessels are partially submerged in 22 feet of water nearly six miles north of the entrance to the St. Clair River, which links Lakes Huron and Erie. Commercial traffic has not been affected because the stricken craft are outside the shipping channel, but the Coast Guard advised mariners in the area to be cautious.

"The Coast Guard will continue to ensure the safety of responders and the public," said Lt. Justin Westmiller, spokesman for the Detroit office.

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